Recently, privacy films are increasingly used for a notebook, a mobile phone, an automated teller machine (ATM), etc., due to privacy protection and security preservation. In addition, privacy films are diversely applied to various fields, such as an immigration checkpoint at airport, a computer room at school, a library, a certificate issuing machine at a ward or village office, and the like.
A privacy film limiting a viewing angle is a film of which light transmittance varies with an incidence angle of light. In general, the light transmittance of the privacy film is highest at a front face of a film, and gradually decreases from the front face to a side face. Therefore, when a privacy film is mounted on a monitor, a user at the front face is able to see the contents displayed on a screen freely but others deviating from the front face (deviating from the front face by 30 or more) can see only a dark and black screen. This makes it possible to prevent information from being leaked out to other person.
Privacy films, which are popularly used at present, are films made and sold by the 3M Company. The privacy films of the 3M Company are made in such a manner that a black material absorbing light and a transparent material transmitting light are alternatingly stacked, and the resultant structure is thinly cut along a direction perpendicular to a stacked direction. According to this method, the black material absorbing light form a predetermined pattern (hereinafter, referred to as ‘black pattern’) and such black patterns are arranged in plurality. Light incident from the front face onto the privacy film can be transmitted, but light incident onto the privacy film at a predetermined angle or more is absorbed into the black pattern and thus cannot be transmitted. Accordingly, the privacy film can provide the viewing angle limiting effect that only a user at the front face can see the contents displayed on the screen, but bystanders deviating from the front face cannot see the contents displayed on the screen.
However, the above method for making a privacy film has several limitations such as process complexity and high fabrication cost because two materials should be alternatingly coated.